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Date: Tue, 25 Aug 2015 17:23:27 +0100
From: Stefan Hajnoczi <stefanha@gmail.com>
Message-ID: <20150825162327.GG8344@stefanha-thinkpad.redhat.com>
References: <1439563931-12352-1-git-send-email-guangrong.xiao@linux.intel.com>
	<1439563931-12352-15-git-send-email-guangrong.xiao@linux.intel.com>
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In-Reply-To: <1439563931-12352-15-git-send-email-guangrong.xiao@linux.intel.com>
Subject: Re: [Qemu-devel] [PATCH v2 14/18] nvdimm: support
	NFIT_CMD_IMPLEMENTED function
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To: Xiao Guangrong <guangrong.xiao@linux.intel.com>
Cc: ehabkost@redhat.com, kvm@vger.kernel.org, mst@redhat.com, gleb@kernel.org, mtosatti@redhat.com, qemu-devel@nongnu.org, stefanha@redhat.com, imammedo@redhat.com, pbonzini@redhat.com, rth@twiddle.net

On Fri, Aug 14, 2015 at 10:52:07PM +0800, Xiao Guangrong wrote:
> @@ -306,6 +354,18 @@ struct dsm_buffer {
>  static ram_addr_t dsm_addr;
>  static size_t dsm_size;
>  
> +struct cmd_out_implemented {

QEMU coding style uses typedef struct {} CamelCase.  Please follow this
convention in all user-defined structs (see ./CODING_STYLE).

>  static void dsm_write(void *opaque, hwaddr addr,
>                        uint64_t val, unsigned size)
>  {
> +    struct MemoryRegion *dsm_ram_mr = opaque;
> +    struct dsm_buffer *dsm;
> +    struct dsm_out *out;
> +    void *buf;
> +
>      assert(val == NOTIFY_VALUE);

The guest should not be able to cause an abort(3).  If val !=
NOTIFY_VALUE we can do nvdebug() and then return.

> +
> +    buf = memory_region_get_ram_ptr(dsm_ram_mr);
> +    dsm = buf;
> +    out = buf;
> +
> +    le32_to_cpus(&dsm->handle);
> +    le32_to_cpus(&dsm->arg1);
> +    le32_to_cpus(&dsm->arg2);

Can SMP guests modify DSM RAM while this thread is running?

We must avoid race conditions.  It's probably better to copy in data
before byte-swapping or checking input values.